3.4. In vitro cytotoxicity
The RPMI8226 cells were selected as a model for in vitro cytotoxicity
study of the Mel-OCM-chitosan conjugates. It was found
in Fig. 6 that free Mel had the maximum inhibition ratio and
all conjugates exhibited obvious cytotoxicity against RPMI8226
cells, indicating polymeric prodrugs did not lose anti-cancer
activity of Mel. At the same time, we can notice a relatively
lower cellular cytotoxicity induced by the polymeric derivatization
of OCM-chitosan and amino acid, which probably due to the
self-assembled behaviors of the amphiphilic polymers to nanoparticles.
Mel was probably chemically embedded in the interior
core of the self-assembled nanoparticles of the conjugates, which
can protect Mel from interaction with the tumor cells. However,
only slight activity loss was observed with the conjugated
form, suggesting that free Mel was released from the conjugates
through cleavage of the amino acid linker between Mel and OCMchitosan.
It is worth noticed that the conjugates with the amino
acid linkers were more active than the conjugates without the
linkers, suggesting the cell cytotoxicity was mainly due to the